This invention generally relates to a novel process for preparing siloxylated metal-containing catalysts and their use in the preparation of urethane foam and elastomers. More particularly, the invention relates to the reaction between silylamines and metallic carboxylates to produce the siloxylated organometallic catalysts.
The prior art discloses two common ways of forming siloxylated metallic bonds: EQU R.sub.3 SiONa+ClM.fwdarw.R.sub.3 SiOM+NaCl (1) EQU .dbd.SiOAc+ROM.fwdarw..dbd.SiOM+ROAC (2)
Although (1) is a fast and complete reaction, it is necessary to remove the sodium chloride since halides are poisonous to many metal catalysts. Also, the sodium silanolate is such a strong base that it can cause unwanted side reactions prior to forming the silanolates or subsequent side reactions due to slight stoichiometric excesses. The reaction designated (2) is generally too slow at temperatures below 100.degree. C. to form siloxylated metallic bonds in situ in urethane reactants. Also this reaction lacks general utility because the temp. necessary for M--O--Si formation is sufficiently high to disproportionate M--O--Si to M--O--M and Si--O--Si, thus catalytic activity would be lost.
In some urethane applications the ideal catalyst system is one in which the active catalyst is formed in the desired time frame in situ. Since in urethane processing there are always multiple components, time is needed to mix the reactants thoroughly and transport them to a mold before reactants start forming high viscosity products.
Previously, U.S. Pat. No. 4,038,221 taught a process for open-celled HR foams utilizing a silicon compound in combination with organometallic catalysts. However, siloxylated metal-containing materials are not disclosed.
With respect to the use of the siloxylated organometallic catalyst, U.S. Pat. No. 3,993,606 disclosed a process for manufacturing a foam having good mold release characteristics. However, the silicone containing compound has Si--CH.sub.2 --N linkages which are too stable to readily react with the metallic material to form siloxylated metallic bonds.
Other references of interest include German Pat. No. 2,524,000 describing silicon-tin compounds as effective condensation catalysts; German Pat. No. 2,404,399 disclosing siloxane compositions and tin as release coatings; German Pat. No. 2,259,802 teaching rebound plastic siloxanes obtained by reacting siloxane in presence of tin carboxylatediethoxydimethylsilanes; USSR Pat. Nos. 509,620 and 319,621 concerning the hardening of the polymeric materials in presence of organostannosiloxanes; and J. Amer. Chem. Soc., 81, 975(1959) which discloses the preparation and properties of some silylalkyl substituted tin compounds.
The prior art, as a whole, does not teach, disclose or suggest the novel process of the present invention which is capable of readily producing siloxylated metal-containing catalysts. The fact that metallic carboxylates of low activity can be mixed with silylamines in situ to form an active siloxylated metallic bond is valuable in that very little reaction is preferred until the mold has been filled at which point very rapid cure is necessary. The siloxylated metal-containing catalysts of the present invention fulfill this criteria.